GREP(1) GENIX Programmer's Manual GREP(1)
NAME
grep, egrep, fgrep - search a file for a pattern
SYNOPSIS
grep [ option ] ... expression [ file ] ...
egrep [ option ] ... [ expression ] [ file ] ...
fgrep [ option ] ... [ strings ] [ file ]
DESCRIPTION
Commands of the grep family search the input files (standard input
default) for lines matching a pattern. Normally, each line found is
copied to the standard output. Grep patterns are limited regular
expressions in the style of ex(1); it uses a compact nondeterminis-
tic algorithm. Egrep patterns are full regular expressions; it uses
a fast deterministic algorithm that sometimes needs exponential
space. Fgrep patterns are fixed strings; it is fast and compact.
The following options are recognized.
-v All lines but those matching are printed.
-x (Exact) only lines matched in their entirety are printed (fgrep
only).
-c Only a count of matching lines is printed.
-l The names of files with matching lines are listed (once)
separated by newlines.
-n Each line is preceded by its relative line number in the file.
-b Each line is preceded by the block number on which it was
found. This is sometimes useful in locating disk block numbers
by context.
-i The case of letters is ignored in making comparisons. (E.g.
upper and lower case are considered identical.) (grep and fgrep
only)
-s Silent mode. Nothing is printed (except error messages). This
is useful for checking the error status.
-w The expression is searched for as a word (as if surrounded by
`\<' and `\>', see ex(1).) (grep only)
-e expression
Same as a simple expression argument, but useful when the
expression begins with a -.
-f file
The regular expression (egrep) or string list (fgrep) is taken
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from the file.
In all cases the file name is shown if there is more than one input
file. Care should be taken when using the characters $ * [ ^ | ( )
and \ in the expression as they are also meaningful to the Shell.
It is safest to enclose the entire expression argument in single
quotes ` '.
Fgrep searches for lines that contain one of the (newline-separated)
strings.
Egrep accepts extended regular expressions. In the following
description `character' excludes newline:
A \ followed by a single character other than newline matches
that character.
The character ^ ($) matches the beginning (end) of a line.
A . matches any character.
A single character not otherwise endowed with special meaning
matches that character.
A string enclosed in brackets [] matches any single character
from the string. Ranges of ASCII character codes may be abbre-
viated as in `a-z0-9'. A ] may occur only as the first charac-
ter of the string. A literal - must be placed where it can't
be mistaken as a range indicator.
A regular expression followed by * (+, ?) matches a sequence of
0 or more (1 or more, 0 or 1) matches of the regular expres-
sion.
Two regular expressions concatenated match a match of the first
followed by a match of the second.
Two regular expressions separated by | or newline match either
a match for the first or a match for the second.
A regular expression enclosed in parentheses matches a match
for the regular expression.
The order of precedence of operators at the same parenthesis level
is [] then *+? then concatenation then | and newline.
SEE ALSO
ex(1), sed(1), sh(1)
DIAGNOSTICS
Exit status is 0 if any matches are found, 1 if none, 2 for syntax
errors or inaccessible files.
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BUGS
Ideally there should be only one grep, but we don't know a single
algorithm that spans a wide enough range of space-time tradeoffs.
Lines are limited to 256 characters; longer lines are truncated.
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